U.S. patent number 8,930,149 [Application Number 13/275,001] was granted by the patent office on 2015-01-06 for relative valuation method for naphtha streams.
This patent grant is currently assigned to Saudi Arabian Oil Company. The grantee listed for this patent is Omer Refa Koseoglu. Invention is credited to Omer Refa Koseoglu.
United States Patent |
8,930,149 |
Koseoglu |
January 6, 2015 |
Relative valuation method for naphtha streams
Abstract
A system and a method for determining the relative value of a
naphtha stream is provided, by reforming the stream into fractions
at a predetermined constant research octane number (RON),
conducting PIONA analysis on the reformate, after which modules or
steps are performed to calculate the feed quality, estimate the
total liquid yields, estimate raw product yields, normalize raw
product yields, determine the value of each fraction based on
predetermined values, and calculate the total value of the naphtha
stream. The method is repeated on samples from different crude oils
in order to provide relative values for comparison purposes at the
predetermined RON.
Inventors: |
Koseoglu; Omer Refa (Dhahran,
SA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Koseoglu; Omer Refa |
Dhahran |
N/A |
SA |
|
|
Assignee: |
Saudi Arabian Oil Company
(Dhahran, SA)
|
Family
ID: |
52117374 |
Appl.
No.: |
13/275,001 |
Filed: |
October 17, 2011 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
61394131 |
Oct 18, 2010 |
|
|
|
|
Current U.S.
Class: |
702/25 |
Current CPC
Class: |
C10G
35/00 (20130101); C10G 32/00 (20130101); C10G
35/24 (20130101); G16Z 99/00 (20190201); C10G
2400/02 (20130101); C10G 2300/305 (20130101); C10G
2300/1044 (20130101) |
Current International
Class: |
G06F
19/00 (20110101) |
Field of
Search: |
;702/25 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Birch, Oil & Gas Journal, Jan. 14, 2002, pp. 54-59 (printed
Jul. 9, 2014 from http://www.ogj.com/articles/print/
volume-100/issue-2/processing/achieving-maximum-crude-oil-value-depends-o-
n-accurate-evaluation.html). cited by applicant .
Pavlovic, Oil & Gas Journal, Nov. 22, 1999, pp. 51-56 (printed
Jul. 9, 2014 from http://www.ogj.com/articles/print/
volume-97/issue-47/in-this-issue/refining/gravity-and-sulfur-based-crude--
valuations-more-accurate-than-believed.html). cited by
applicant.
|
Primary Examiner: Bui; Bryan
Attorney, Agent or Firm: Abelman, Frayne & Schwab
Parent Case Text
RELATED APPLICATION
This application claims the benefit of U.S. Provisional Patent
Application No. 61/394,131 filed Oct. 18, 2010, the disclosure of
which is hereby incorporated by reference.
Claims
I claim:
1. A system for determining the relative value of a stream of
treated naphtha based upon a separately provided PIONA analysis of
the fractions of the naphtha after processing in a reformer that is
operated at a severity that yields a gasoline product having a
predetermined constant research octane number, the system
comprising: a memory that stores calculation modules and data; a
processor coupled to the memory; a calculation module that
calculates the feed quality of the naphtha fractions; a calculation
module that estimates the total liquid products variable from the
feed quality and the constant research octane number data; a
calculation module that estimates raw product yields of methane,
ethane, propane, butane and gasoline from the total liquid products
variable; a calculation module that determines raw product yields
of hydrogen from the total liquid products variable and the
predetermined constant research octane number (RON); a calculation
module that adds the raw product yields of methane, ethane,
propane, butane, gasoline and hydrogen to derive a raw product
total yield; a calculation module that normalizes the estimated
yields for losses of hydrogen, methane, ethane, propane, butane and
gasoline, as a percentage of the raw product total yield; a
calculation module that derives the value of the normalized
estimated yields of hydrogen, methane, ethane, propane, butane and
gasoline by multiplying each normalized estimated yield by a
predetermined unit value of each product; and a calculation module
that produces and displays an estimated value of the naphtha stream
by totaling the values of the normalized estimated yields of
hydrogen, methane, ethane, propane, butane and gasoline.
2. The system of claim 1 in which the treated naphtha stream
contains less than 0.5 ppmw of sulfur and less than 0.5 ppmw
nitrogen.
3. The system of claim 1 in which the treated naphtha stream is
straight run naphtha from a hydroprocessor.
4. The system of claim 1 in which the RON is selected from the
range of from 95 to 100.
5. The system of claim 4 in which the RON is selected from the
range of from 95 to 98.
6. A method for operating a computer to determine the relative
value of a treated naphtha stream derived from a crude oil sample
obtained from a particular source, the method comprising: entering
into the computer data obtained by PIONA analysis of the fractions
of the naphtha stream that is processed in a reformer operated
under conditions that produce a gasoline product having a
predetermined constant research octane number; calculating the feed
quality of the naphtha fractions; estimating the total liquid
products variable from the feed quality and the constant research
octane number; estimating raw product yields for methane, ethane,
propane, butane and gasoline from the total liquid products
variable; determining raw product yields for hydrogen from the
total liquid products variable and the predetermined constant
research octane number; adding the raw product yields for methane,
ethane, propane, butane, gasoline and hydrogen to derive a raw
total yield; normalizing the estimated yields of hydrogen, methane,
ethane, propane, butane and gasoline, as a percentage of the raw
total yield; calculating the value of the normalized estimated
yields of hydrogen, methane, ethane, propane, butane and gasoline
by multiplying each normalized estimated yield by a predetermined
unit value for each; calculating an estimated value of the naphtha
stream as the total obtained by adding the values of the normalized
estimated yields of hydrogen, methane, ethane, propane, butane and
gasoline; and displaying and storing the calculated estimated value
of the treated naphtha.
7. The method of claim 6 in which the treated naphtha stream
contains less than 0.5 ppmw of sulfur and less than 0.5 ppmw of
nitrogen.
8. The method of claim 6 in which the treated naphtha stream is
straight run naphtha from a hydroprocessor.
9. The method of claim 6 in which the RON is selected from the
range of from 95 to 100.
10. The method of claim 6 which includes the further steps of
entering PIONA analyses from a plurality of samples derived from
different crude oils and compiling the calculated estimated values
for each of the treated naphthas to provide a listing of
comparative values based upon a constant RON.
Description
FIELD OF THE INVENTION
This invention relates to a method and process for the evaluation
of naphtha derived from crude oil based on its composition and
processability.
BACKGROUND OF THE INVENTION
There are more than 200 crude oils produced and traded worldwide.
Crude oils are very complex mixtures of many thousands of different
hydrocarbons. Depending on the source, the oils contain various
proportions of straight and branched-chain paraffins,
cycloparaffins, and naphthenic, aromatic and polynuclear aromatic
hydrocarbons. The nature of the crude oil governs, to a certain
extent, the nature of the products that can be manufactured from it
and their suitability for specific applications.
Worldwide supply and demand, regional refining capacities and
configurations, and crude composition are the key factors that
determine the value of crude oil. The first factor is purely
market-dependent and cannot be predicted from the crude oil
quality. Accordingly, the crude oil value is determined by the
regional crude market and differentials such as freight, quality
adjustments, refining cost and competitive pricing.
In a typical petroleum refinery, crude oil is first distilled under
atmospheric pressure. Gases will rise to the top of the
distillation column, followed by lower boiling liquids, including,
naphtha, kerosene and diesel oil. Naphtha is not a final product,
but is subjected to additional treatment steps, such as
hydrotreating and catalytic reforming to produce reformate. The
reformate is then sent to a gasoline pool for blending.
An article by Colin Birch, "Achieving Maximum Crude Oil Values
Depends on Accurate Evaluation," Oil & Gas Journal, Vol. 100,
Issue 2 (Jan. 14, 2002), describes a number of evaluation methods
for obtaining an objective calculation of the value of a specific
crude oil from a particular source. Summaries of several of these
methods follow.
Bulk-Property Method: This method correlates actual crude value
with bulk properties. API gravity and sulfur content are widely
used for the correlation, and other bulk properties, such as
viscosity and pour point, can also be used. This method is
relatively simple in terms of the amount of testing required.
However, this method may not be reliable when a large range of
crudes are being valued. For example, some of the naphthenic crudes
may be valued relatively higher, using this method, but this result
may not reflect the actual market value for the crude oil.
Refining-Value Method: Crude oils are evaluated and valued using
the refinery yields and process operating costs for each crude
stream, typically using a linear program (LP) or other model.
Refinery models require detailed physical property information and
distillation cuts as determined by a detailed crude oil assay.
Process yields and operating costs are used with appropriate
product values to calculate refining-value differentials between
the crude oils. The refining-value method simulates the process
used by refiners for selecting crude oils. Detailed crude oil
quality information and the need to run a refinery model for a
given refinery to generate the yields make this method more complex
than the bulk-property method. If input stream quality changes
significantly, a new set of yields must be generated. In relatively
simple systems involving only a few crudes with reasonably stable
quality, the refining-value method normally provides the most
accurate value allocation for a refiner.
Distillation-Yield Method: This is a simplified version of the
refining-value method, which instead of using a linear program or
other model will only use the yield of each fraction. These product
yields from distilling each crude are used with product values to
calculate the relative value of each crude. In many cases, some
physical properties of the distillation cuts are used in the
value-adjustment system. The quality information from each crude is
relatively simple and includes distillation yields and distillation
cut properties. The distillation yield-method is more complex than
the bulk-property method, but less complex than the refining-value
method. Because it uses product values in the calculation,
reliability of crude oil value data is not an issue. The products
being valued, however, such as naphtha, are not finished products
meeting defined specifications. So there is some uncertainty
regarding the value adjustment for key properties of the
distillation cuts.
Several properties of naphtha streams can be evaluated, including
API gravity, sulfur, nitrogen, carbon and hydrogen contents, and
research octane number. Research octane number is the measure of a
fuel's ability to prevent detonation in a spark-ignition engine.
Measured in a standard single-cylinder, variable-compression-ratio
engine by comparison with primary reference fuels, American
Standard Testing Material Tests ASTM D-2699 and ASTM D-2700
describe the determination of research and motor octane numbers,
respectively. Under mild conditions, the engine measures research
octane number (RON), while under sever conditions the engine
measures motor octane number (MON). Where the law requires posting
of octane numbers on dispensing pumps, the antiknock index (AKI) is
used. This is the arithmetic average of RON and MON, namely,
(R+M)/2. It approximates the road octane number, which is a measure
of how an "average" car responds to fuel. It is the most critical
property for naphtha/gasoline streams.
It is very difficult to evaluate the naphtha streams based on their
hydrocarbon distributions. Rather, all the naphtha fractions must
be brought to a commercial product stream for evaluation
purposes.
The RON of a spark-ignition engine fuel is determined using a
standard test engine and operating conditions to compare its knock
characteristic, defined as knock intensity (K.I.) with those of
primary reference fuel (PRF) blends (containing iso-octane and
normal heptane) of known octane number. For example, an 87-octane
gasoline has the same octane rating as a mixture of 87% iso-octane
and 13% n-heptane. Compression ratio (CR) and fuel-air ratio are
adjusted to produce standard K.I. for the sample fuel, as measured
by a specific electronic detonation meter instrument system. A
standard K.I. guide table relates engine CR to octane number level
for this specific method. The fuel-air ratio for the sample fuel
and each of the primary reference fuel blends is adjusted to
maximize K.I. for each fuel. While gasoline will have an RON of 85
or higher, naphtha will have an RON below 60.
The MON of a spark-ignition engine fuel is determined using a
standard test engine and operating conditions to compare its knock
characteristic with those of PRF blends of known octane number. CR
and fuel-air ratios are adjusted to produce standard K.I. for the
sample fuel, as measured by a specific electronic detonation meter
instrument system. A standard K.I. guide table relates engine CR to
octane number level for this specific method. The fuel-air ratio
for the sample fuel and each of the PRF blends is adjusted to
maximize K.I. for each fuel.
Therefore, a need exists for an improved system and method for
determining the value of crude oils from different sources that can
be objectively applied to compare the naphtha fractions from
different sources.
A further object is to provide a system and method that can be
applied, for example, to compare two streams in order to ascertain
which stream has a higher value based upon the current value for
its constituent fractions in order to give the refiner a basis for
deciding which stream should be processed first.
Another object of this invention is to provide a method for
evaluation of particular naphtha streams derived from crude oils
from various sources to establish an objective basis for economic
comparison based on specific value.
In the following description, the terms "reformer unit", "reformer"
and "reforming unit" are used interchangeably, and refer to
conventional apparatus used in a catalytic reforming process.
SUMMARY OF THE INVENTION
The above objects and further advantages are provided by the
invention which broadly comprehends a system and a method for
determining the value of a naphtha stream by reforming the stream
into fractions having a constant research octane number; the
fractions are then evaluated by an algorithm, and an evaluation is
obtained for the stream. When the method is applied to naphtha
streams derived from crude oils from various sources, the
respective value provides an objective basis for relative
evaluation of the crude oil.
The system and method of the invention can be utilized to valuate
naphtha fractions derived from crude oils, which fractions have
nominal boiling points in the range of -11.5 to 235.degree. C., and
more preferably from 36-180.degree. C. Naphtha fractions vary in
composition and, as a result, octane number, which, as discussed
above, is a key indicative property for engine-knocking
characteristic. In a preferred embodiment, the comparative
evaluation method is practiced on straight run naphtha samples. The
difference in composition and properties make the evaluation of the
naphtha fraction difficult.
In the method of the present invention, a catalytic reforming
process is used to convert the naphtha with varying research octane
numbers into straight run naphtha fractions, including reformate at
a constant research octane. Having been brought to a commercial
product stream, the reformate can now be efficiently valued. The
reformate is fed into a gas chromatograph that is used to obtain an
analysis of its component paraffins, iso-paraffins, olefins,
iso-olefins, naphthenes and aromatics, i.e., to provide a PIONA
analysis. An algorithm is applied to the total percentages of the
naphthenes and aromatics in order to determine a value of the
naphtha stream. The value of each of the components is assigned
based upon independently determined values at a given time and
place that can be predetermined by the user.
The method and system of the invention can be applied to samples
derived from different crude oils obtained from different
reservoirs or regions to provide relative values for the same RON
in order to provide refiners with a basis for comparison in the
market(s) in which their products are sold.
BRIEF DESCRIPTION OF THE DRAWINGS
Further advantages and features of the present invention will
become apparent from the following detailed description of the
invention when considered with reference to the accompanying
drawing, in which:
FIG. 1 schematically illustrates the hydrotreating and reformation
of naphtha and the chromatograph analysis of the resultant
streams;
FIG. 2 is a process flow diagram of additional steps carried out to
establish a value for naphtha streams using the system and method
of the present invention; and
FIG. 3 is a block diagram of a component of a system for
implementing the invention for establishing a value for naphtha
streams, according to one preferred embodiment of the present
invention.
DETAILED DESCRIPTION OF INVENTION
Reference will now be made in detail to implementation of the
invention, examples of which are illustrated in the accompanying
drawings.
FIG. 1 shows the hydrotreating and reforming process 100. Naphtha
stream 110 is fed into a hydrotreater 115 to separately reduce
sulfur levels below 0.5 ppmw, and to likewise reduce nitrogen
levels below 0.5 ppmw. The maximum allowable sulfur and nitrogen
contaminant content levels must be maintained within the
predetermined limits established for the efficient use of the
reformer unit catalyst. The reformer catalyst is made of noble
metals such as platinum and palladium and is very sensitive to
impurities like sulfur and nitrogen. The presence of higher levels
of sulfur and nitrogen during the operation will poison the
catalyst. As is known to those of ordinary skill in the art, the
major sources of sulfur are inadequate hydrotreating, hydrotreating
stripper upsets and the recombination of hydrogen sulfide and
olefins at high temperature and low pressures. The principal
sources of nitrogen are inadequate hydrotreating, cracked naphtha
in the feedstock, and improper use of inhibitors. Since the
reforming unit catalyst is very sensitive to impurities, it is
critical to the successful practice of the evaluation method that
the sulfur and nitrogen levels be reduced in the hydrotreating
process to provide a reformer feedstream meeting the
specification.
The hydrotreated naphtha stream 120 is then fed into a reformer
125, where it is reformed into streams of hydrogen ("H2") 130,
methane ("C1") 135, ethane ("C2") 140, propane ("C3") 145, butane
("C4") 150, and reformate ("C5+") 155. The reformer 125 is operated
at a severity to yield reformate having a constant research octane
number, for example, a target RON of 98 can be selected. Thus,
while the product yield distribution will differ for each naphtha
feedstock produced, the quality of gasoline, as measured by the
research octane number, will be uniform.
The predetermined octane number selected can be in the range of
from 80 to 100 for products coming from the reforming unit. A more
preferred value is in range of from 95 to 100, and the most
preferred is in the range of from 95 to 98, which is the gasoline
RON specification. It is to be noted that the yield declines with
an increase in the target octane number.
The separated light gases are fed into one or more refinery gas
analyzers 160, which are gas chromatographs that will analyze the
gases in accordance with ASTM D1945. This analysis is not within
the scope of the present invention.
The liquid reformate 155 is fed into PIONA analyzer 165, a gas
chromatograph that will analyze the liquid in accordance with ASTM
D6839. In the PIONA analysis, fractions of the reformate are
tabulated by carbon number and n-paraffins, i-paraffins, naphthenes
and aromatics, showing the percentage volume for each carbon
number. As the reformate is derived from straight-run naphtha from
crude oil distillation, as opposed to being derived from
intermediate refinery naphtha from cracking reactions, no or few
olefins are present. A typical PIONA analysis is shown in Table 1.
Note that while most of the propane and butane present in the
hydrotreated naphtha 120 is separated by the reformer 125 into
streams 145 and 150, some propane and butane will remain dissolved
in the liquid reformate product 155, and thus will appear in the
PIONA analysis.
TABLE-US-00001 TABLE 1 EXAMPLE OF A PIONA ANALYSIS OF A NAPHTHA
STREAM Hydrocarbon Family Carbon # n-Paraffins i-Paraffins
Naphthenes Aromatics C3 0.112% 0% 0% 0% C4 2.022% 0.212% 0% 0% C5
6.232% 2.626% 0.494% 0% C6 8.697% 6.114% 3.086% 0.751% C7 12.749%
16.033% 5.545% 1.985% C8 5.288% 6.006% 3.017% 2.448% C9 3.02%
3.829% 2.019% 1.893% C10 1.304% 2.159% 0.819% 0.968% C11 0.084%
0.25% 0.221% 0.017% Total* 37.29% 36.77% 14.98% 8.05% *Total =
97.09 V %, losses = 2.91 V %. (i.e., the yields are not
normalized.)
FIG. 2 shows a preferred embodiment of the present invention,
representing a process flowchart of steps that occur after the
PIONA analysis is completed and the results are tabulated. Variable
N is used to represent the total percentage of naphthenes by
volume, and variable A is used to represent the total percentage of
aromatics by volume, as derived from the PIONA analysis.
In step 220, the feed quality is calculated as: Feed quality=N+2A
(1)
Thus, in the example given in Table 1, N=14.98, A=8.05, and
therefore the feed quality, N+2A=14.98+2*8.05=31.08.
Equations for determining the total reformer yield were developed
from a linear regression of the N+2A concentration versus total
yield. The individual yields for H2, C1, C2, C3, C4 and C5+ and the
reformate yield were then calculated from a linear regression of
the total reformate yield versus individual yields at the targeted
octane number.
In step 230, the total liquid yield, Y, is estimated as a function
of the feed quality and the constant RON number (i.e., the target
number), Rt: Y=KYa*(N+2A).sup.2+KYb*(N+2A)+KYc*Rt.sup.2+KYd*Rt+KYe
(2)
where KYa through KYe are constants. In a preferred embodiment,
KYa=-0.01702; KYb=2.192; KYc=-0.03333; KYd=5.531; and
KYe=-206.63.
Thus, for the example given in Table 1, when a target octane number
for gasoline of 98 is selected, the equation is as follows:
Y=(-0.01702)*(31.08).sup.2+2.192*31.08-0.03333*(98).sup.2+5.531*98-206.63-
; or Y=66.99.
In step 240, the estimated raw product yields for methane, ethane,
propane, butane and gasoline are modeled linearly based upon the
total liquid products variable, while hydrogen is modeled linearly
based upon the total liquid products variable and the constant RON
number, Rt, as follows: Raw Methane Yield, C1r=KC1ra*Y+KC1rb (3)
Raw Ethane Yield, C2r=KC2ra*Y+KC2rb (4) Raw Propane Yield,
C3r=KC3ra*Y+KC3rb (5) Raw Butane Yield, C4r=KC4ra*Y+KC4rb (6) Raw
Gasoline Yield, Gr=KGra*Y+KGrb (7) Raw Hydrogen Yield,
Hr=KHra*Y+KHrb*Rt+KHrc (8) where KC1ra through KC4rb, KGra, KGrb,
and KHRA through KHrc are constants derived by linear regression
analysis. In a preferred embodiment, KC1ra=-0.12393; KC1rb=11.42;
KC2ra=-0.17991; KC2rb=16.8; KC3ra=-0.25714; KC3rb=24.24286;
KC4ra=-0.28705; KC4rb=27.27143; KGra=0.839255; KGrb=18.09532;
KHra=0.0605; KHrb=0.1; and KHrc=-12.145.
Thus, for the example given in Table 1:
C1r=-0.12393*66.99+11.42=3.11 C2r=-0.17991*66.99+16.8=4.75
C3r=-0.25714*66.99+24.24286=7.02 C4r=-0.28705*66.99+27.27143=8.04
Gr=0.839255*66.99+18.09532=74.32
Hr=0.0605*66.99+0.1*98-12.145=1.71
The estimated total raw yield is the sum of the estimated raw
yields for these components: Total Raw Yield,
Tr=C1r+C2r+C3r+C4r+Gr+Hr (9)
Thus, in the present example,
Tr=3.11+4.75+7.02+8.04+74.32+1.71=98.95
In step 250, the yields are normalized to 100 by dividing the
individual raw yields by the total raw yields, as follows:
Normalized Methane Yield, C1n=(C1r*100)/Tr (10) Normalized Ethane
Yield, C2n=(C2r*100)/Tr (11) Normalized Propane Yield,
C3n=(C3r*100)/Tr (12) Normalized Butane Yield, C4n=(C4r*100)/Tr
(13) Normalized Gasoline Yield, Gn=(Gr*100)/Tr (14) Normalized
Hydrogen Yield, Hn=(Hr*100)/Tr (15)
Thus, for the example given in Table 1,
C1n=(3.11*100)/98.94917=3.14 C2n=(4.75*100)/98.94917=4.80
C3n=(7.02*100)/98.94917=7.09 C4n=(8.04*100)/98.94917=8.13
Gn=(74.32*100)/98.94917=75.11 Hn=(1.71*100)/98.94917=1.73
In step 260, the estimated yield of each fraction is multiplied by
its unit value, to provide the value of each fraction: Value of
Methane, C1v=(C1n/100)*C1P, where C1P is methane's value (16) Value
of Ethane, C2v=(C2n/100)*C2P, where C2P is ethane's value (17)
Value of Propane, C3v=(C3n/100)*C3P, where C3P is propane's value
(18) Value of Butane, C4v=(C4n/100)*C4P, where C4P is butane's
value (19) Value of Gasoline, Gv=(Gn/100)*GP, where GP is
gasoline's value (20) Value of Hydrogen, Hv=(Hn/100)*HP, where HP
is hydrogen's value (21)
Thus, if unit values are, for methane, C1P=$152.44/ton; for ethane,
C2P=$149.81/ton; for propane, C3P=$343.71/ton; for butane,
C4P=$499.03/ton; for gasoline, GP=$601.63/ton; and for hydrogen,
HP=$391.60/ton, then the value of those products in the naphtha
stream of Table 1 would be calculated as:
C1v=(3.14/100)*$152.44/ton=$4.80/ton
C2v=(4.80/100)*$149.81/ton=$7.19/ton
C3v=(7.09/100)*$343.71/ton=$24.37/ton
C4v=(8.13/100)*$499.03/ton=$40.57/ton
Gv=(75.11/100)*$601.63/ton=$451.88/ton
Hv=(1.73/100)*$391.60/ton=$6.77/ton
In step 270, the total value of the naphtha stream is then
estimated by summing the calculated values of the individual
streams: Naphtha Unit Value ($/ton), NPT=C1v+C2v+C3v+C4v+Gv+Hv
(22)
For the example given in Table 1, the value of the naphtha stream
calculated by this method is:
NPT=4.80+7.19+24.37+40.57+451.88+6.77, or NPT=$535.58/ton.
The value of the naphtha stream can also be restated as $/barrel,
by dividing the value expressed as $/ton by the density and
multiplying by the number of liters in a barrel of oil (159
liters/barrel): NPB=(NPT/Density)*159 liters/barrel (23)
For the example given in Table 1, with a density of 750 liters/ton,
NPB=($535.58/ton/750 liters/ton)*159
liters/barrel=$113.54/barrel.
When two naphtha streams are to be evaluated, this process can
readily be used to calculate the value of one stream relative to
the other.
FIG. 3 illustrates one embodiment of the present invention,
implemented in a computer system 300, with a number of modules.
Computer system 300 includes a processor 310, such as a central
processing unit, an input/output interface 320 and support
circuitry 330. In certain embodiments, where the computer 300
requires direct human interaction, a display 340 and an input
device 350 such as a keyboard, mouse or pointer are also provided.
The display 340, input device 350, processor 310, input/output
interface 320 and support circuitry 330 are shown connected to a
bus 360 which also connects to a memory unit 370. Memory 370
includes program storage memory 380 and data storage memory 390.
Note that while computer 300 is depicted with the direct human
interface components of display 340 and input device 350,
programming of modules and importation and exportation of data can
also be accomplished over the interface 320, for instance, where
the computer 300 is connected to a network and the programming and
display operations occur on another associated computer, or via a
detachable input device, as are well known in the art for
interfacing programmable logic controllers.
Program storage memory 380 and data storage memory 390 can each
comprise volatile (RAM) and non-volatile (ROM) memory units and can
also comprise hard disk and backup storage capacity, and both
program storage memory 380 and data storage memory 390 can be
embodied in a single memory device or separated in plural memory
devices. Program storage memory 380 stores software program modules
and associated data. Data storage memory 390 stores data used
and/or generated by the one or more modules of the present
invention.
It is to be appreciated that the computer system 300 can be any
general or special purpose computer such as a personal computer,
minicomputer, workstation, mainframe, a dedicated controller such
as a programmable logic controller, or a combination thereof. While
the computer system 300 is shown, for illustration purposes, as a
single computer unit, the system can comprise a group/farm of
computers which can be scaled depending on the processing load and
database size, e.g., the total number of samples that are processed
and results maintained on the system. The computer system 300 can
serve as a common multi-tasking computer.
The computing device 300 preferably supports an operating system,
for example, stored in program storage memory 390 and executed by
the processor 310 from volatile memory.
The system and method of the present invention have been described
above and with reference to the attached drawings; however,
modifications will be apparent to those of ordinary skill in the
art and the scope of protection for the invention is to be defined
by the claims that follow.
* * * * *
References